Television shows like ABC's "Modern Family" have gained attention for the creation of gay characters that also raise children, but just how common is that? Census data from 2010 is giving experts a glimpse for the first time into the number of American same-sex households where children are being raised.

It is estimated that approximately one-quarter of all same-sex households in the United States are raising children, according to data that is being analyzed and revealed for only a few states at a time.

In California, 21 percent of same-sex couples were found to be raising children. In Delaware, Kansas, Pennsylvania, and Wyoming, the percentages were 19, 26, 20, and 28 percent, respectively, according to the Williams Institute, which released the data this week.

According to ABC News, Stuart Gaffney of Marriage Equality USA stated that this information is invaluable for those who support same-sex marriage who are trying to prove a point to lawmakers. “This is the first time it accurately reflects families that have always been there,” he said.

The numbers, he argued, don't allow lawmakers to ignore the fact that they have same-sex constituents who want to start families.

But many, particularly evangelicals, have made the case that families should have both a mom and a dad.

Peter Sprigg, senior fellow for policy studies at Family Research Council, has argued that more children would grow up fatherless and birth rates would fall with an increase in same-sex households.

“Research clearly demonstrates that family structure matters for children, and the family structure that helps the most is a family headed by two biological parents in a low-conflict marriage,” he said, citing research group Child Trends.

Earlier this year, a study on “Family Structure and Children’s Health in the United States,” released by the Centers for Disease Control and Prevention, revealed that children raised by their own mother and father, who are married, are happier (experience better mental health), healthier (have better physical health), and more prosperous (attain higher socioeconomic status) than children raised in any other household setting.

The Williams Institute is a UCLA school of law and national think tank whose mission is to help advance gay rights laws and public policies through research and scholarship. It first released a report last week on Hawaii and Alabama, where 27 and 23 percent of same-sex households, respectively, were raising children together.

This new information could serve as fuel in the New York legislature's battle over whether or not to allow same-sex marriage in their state, which may come to a conclusion today.

According to the Williams Institute, approximately 14,000 children are being raised by about 7,200 same-sex couples in the state of New York. If the Empire State should decide to allow gay marriage, it would be the largest of any such state in terms of population and, as a result, over a tenth of the American population would then live in a state where same-sex couples can be married.

Currently, gay marriage is legalized in five states plus the District of Columbia, while four states allow civil unions between same-sex couples.

The Williams Institute says that past studies indicate that there may be more same-sex couples than the 2010 Census will actually show. On June 30, the think tank is set to release more information on the next five states – Alaska, Colorado, Connecticut, Nebraska, and North Carolina – to the public.